There are various types of solid preparation printing apparatuses that can be used as an apparatus for printing letters or characters, marks, and the like on the surface of a solid preparation such as a tablet. In the printing apparatus, a transfer printing is performed on a solid preparation using a roller provided with a transferred pattern on its surface. When the printing is completed, whether the printing is acceptable or not is determined with an imaging device, a determination device, or the like.
Incidentally, some solid preparation (hereinafter referred to as “tablet”) to be printed have a split line. When printing is performed on a tablet having a split line, it is required to avoid such a printing defect that the print overlaps the split line. In order to fulfill this requirement with a conventional printing apparatus, all tablets being conveyed have to be arranged such that their split lines are oriented to a certain direction (for example, the conveyance direction) with respect to the conveyance direction, and the surface having the split line have to face up (or down). If the direction of the split line deviates from a certain direction, a printing defect as described above occurs. The number of defects reaches several hundred thousand per hour.